NA TURE 



[June 2, 1904 



issued a translation, by Prof. G. Siebert, of Mr. F. Soddy's 

 Wilde lecture (see Nature, March 3, p. 418) on the evolu- 

 tion of matter as revealed by the radio-active elements. 

 A translation, by Mr. E. Ruhmer, of a lecture by Mr. W. J. 

 Hammer, delivered before the American Institute of 

 Electrical Engineers, on radium and other radio-active sub- 

 stances, has been issued by the publishers of T>er 

 Mechaniker, Berlin. 



OUR ASTRONOMICAL COLUMN. 



The Extreme Ultra-Violet Spectrum of Hydrogen. — 

 In No. 4, vol. xix., of the Astrophysical Journal, Mr. 

 Theodore Lyman, of Harvard University, gives a list of 

 wave-lengths for the lines in the extreme ultra-violet spec- 

 trum of hydrogen, first discovered by Dr. Victor Schumann. 

 In Mr. Lyman's experiments the light from the discharge 

 tube was transmitted through fluorite windows and a tube 

 containing hydrogen at very low pressure, and the spectrum 

 was formed by a concave grating ruled on speculum metal. 

 He found that from the region about A 1854 to about A 1700 

 the spectrum is almost continuous, containing only a few 

 faint lines. About A 1700 there is an absorption band, the 

 width of which seems to depend upon the purity of the 

 hydrogen enclosed in the apparatus. Beyond A 1650, to- 

 wards the more refrangible limit of the spectrum, numerous 

 fine lines exist, and of these Mr. Lyman has measured 134. 

 In the table accompanying the paper the wave-lengths (to 

 five figures) and intensities of 133 lines between A 1033 'ind 

 A 1878 are given. It is interesting to note that the superior 

 reflecting power of speculum metal for these short wave- 

 lengths has been incidentally demonstrated by the use of 

 the grating. 



Varlable Radlal \"elocitv of 7) PisciUM. — A series of 

 spectrograms of r; Piscium obtained by Prof. H. C. Lord, 

 of Columbus (Ohio), and extending over the period 

 December, iqoi, to January, 1904, indicate that this star 

 has a variable radial velocity of long period. 



From measurements of H7 and thirteen carefully selected 

 iron lines the following results, among others, were 

 obtained : — 



The sharp definition of the lines in the spectrum of 

 ■n Piscium render its radial velocity especially suitable for 

 spectroscopic measurement, and this fact, with other con- 

 firmatory evidence, leads Prof. Lord to the conclusion that 

 the variabilitv is real {Astrophvsical Journal, No. 4 vol. 

 xix.). 



Proposed New Observ.\tories. — In a report published 

 by the Carnegie Institution at Washington (December, 

 1903), a committee consisting of Profs. Boss, Campbell and 

 Hale, which was appointed by that institution " to consider 

 certain large projects in astronomy," stronglv urge the 

 establishment of an observing station in the southern hemi- 

 sphere for the prosecution of certain definite observations 

 which it is hoped might be completed in ten or twelve years. 

 They also recommend that an observing station for' solar 

 investigations in an exceptionally favourable atmosphere 

 should be established and maintained throughout one full 

 sun-spot period (eleven years) at least. Further, they urge 

 the construction and maintenance of a large reflector for 

 astrophysical investigations at one, or both, of the proposed 

 stations. These recommendations are supplemented by a 

 detailed programme of the work that might be accomplished 

 and a carefully prepared scheme for the necessary buildings 

 and staffs. 



In Appendix A Prof. J. W. Hussey, who was deputed to 

 explore California and Arizona in order to determine the 

 most suitable site for the proposed solar observatory, gives 

 NO. 1805, VOL. 70] 



an interesting account of his search, which led to the re- 

 commendation of Mount Wilson (California) as offering the 

 best facilities for the work. Appendix B consists of a 

 number of letters from eminent astronomers in answer to a 

 confidential inquiry as to their views on the establishment 

 of the proposed observatories. 



Varhrilitv of Spark Spectra. — Some interesting results 

 have been obtained by Mr. A. S. King, of Bonn, from a 

 long series of experiments on the variability of spark spectra 

 with various conditions of current, discharge and environ- 

 ment. So far, the spark spectra of six metals, Cd, Zn, Mg, 

 Ca, Hg and Al, have been studied under different conditions, 

 and the results of the experiments have led to the following 

 conclusions : — 



(i) The lines of each metal may be divided into two groups 

 according to their behaviour when the conditions are varied. 

 The first group contains all the " series " lines and a few 

 others, whilst the second group includes the lines for which 

 no " series " relations have vet been discovered. (2) The 

 lines of both groups are enhanced by capacity and weakened 

 by self-induction, but those of the second group are much 

 more affected in this way than those of the first. (3) Of 

 the two " subseries " of each metal the first is much more 

 sensitive to all changes. (4) The last members of a series 

 are reduced more by self-induction than the first, a shift of 

 maximum intensity towards the greater wave-lengths being 

 produced. " Capacity " has the opposite effect. 



Mr. King describes his experiments, and discusses the 

 results in detail in a paper published in No. 4, vol. xix., of 

 the Astrophysical Journal, where some of his photographs 

 are reproduced. 



Report of the Oxford University Observatory. — In 

 the twentj'-ninth annual report of the Oxford University 

 Observatory, Prof. H. H. Turner gives a n'siime of the 

 work accomplished during the twelve months from May i, 

 1903, to April 30, 1904. He again refers to the urgent need 

 for a residen.'~e attached to the observatory, but on account 

 of the general lack of funds at the university he does not 

 press the matter. 



The measureinent and reduction of the plates for the 

 Oxford section of the International Astrographic Chart is 

 now complete, and the press copy of the work has been 

 lodged at the Bodleian Library for safety until it is possible 

 to raise the 2000?. necessary for its printing and publication. 

 It was proposed that the experience gained bv the observ- 

 atory staff in the production of this work might be utilised 

 in measuring the plates taken at one of the southern observ- 

 atories where the lack of funds and instruments prohibits 

 the completion of the work. To this end fifty plates were 

 received from the Perth (W. -Australia) Observatory, and on 

 measuring twenty-one of them it was found that their re- 

 duction could be easilv and economicallv carried out at 

 Oxford. 



A stereo-coiTiparator, w-hich is essentially an elaborate 

 and improved stereoscope for the comparison of the star- 

 places on any two plates of the same region, but taken at 

 different epochs, has been presented to the observatory by 

 Mr. C. L. Brook, and has been proved to be efficient and 

 easily manipulated. 



The Stereo-Compar.^tor. — In No. 5, vol. xii., of Popular 

 Astronomy, there appears a translation of a paper com- 

 municated to the Astronomical Society of Belgium by Dr. 

 G. van Biesbroeck, in which the author traces the 

 evolution of, and describes, the stereo-comparator invented 

 by Dr. Pulfrich ; he also gives brief accounts of the re- 

 searches wherein the instrument will prove to be an 

 extremely useful aid. Amongst the latter he notices the 

 study of cometary features, the detection of stellar proper 

 motions, and the discovery of minor planets. As evidence 

 of the comparator's efficacy in the last named field, he 

 mentions that Dr. Pulfrich, who was totally without ex- 

 perience in minor planet work, not only found several 

 asteroids which Prof. Wolf had recognised on a pair of 

 plates taken at Heidelberg, but also discovered a new one, 

 which the careful scrutiny of the latter observer, under the 

 ordinary conditions, had failed to reveal. 



